Overview

TestDriver provides custom error classes with rich debugging information. These are exported from the SDK and can be used for instanceof checks in your tests.

javascript

import TestDriver, { ElementNotFoundError, AIError } from 'testdriverai';

ElementNotFoundError

Thrown when find() cannot locate an element on screen, or when calling click()/hover() on an unfound element.

javascript

try {
  await testdriver.find('nonexistent button').click();
} catch (error) {
  if (error instanceof ElementNotFoundError) {
    console.log(error.description);       // "nonexistent button"
    console.log(error.screenshotPath);    // path to debug screenshot
    console.log(error.pixelDiffPath);     // path to pixel diff image
  }
}

Properties

<ParamField path="name" type="string"> Always `"ElementNotFoundError"`. </ParamField> <ParamField path="message" type="string"> Enhanced message with a debug block containing element description, cache status, similarity scores, and AI response details. </ParamField> <ParamField path="description" type="string"> The original element description passed to `find()`. </ParamField> <ParamField path="screenshotPath" type="string | null"> Absolute path to a debug screenshot saved at the time of failure. Written to `<os.tmpdir>/testdriver-debug/screenshot-<timestamp>.png`. </ParamField> <ParamField path="pixelDiffPath" type="string | null"> Absolute path to a pixel diff image showing the comparison between the cached and current screenshots. Written to `<os.tmpdir>/testdriver-debug/pixel-diff-error-<timestamp>.png`. Only present when cache was involved. </ParamField> <ParamField path="cachedImagePath" type="string | null"> URL to the cached image that was compared against. </ParamField> <ParamField path="aiResponse" type="object | null"> Sanitized AI response object. Large binary fields (`croppedImage`, `screenshot`, `pixelDiffImage`) are removed. Contains cache metadata like `similarity`, `cacheHit`, `cacheStrategy`, `cacheDiffPercent`, and `threshold`. </ParamField> <ParamField path="timestamp" type="string"> ISO 8601 timestamp of when the error was created. </ParamField>

Enhanced Message

The error message is automatically enhanced with debugging information:

code

Element not found: "submit button"

=== Element Debug Info ===
Element: submit button
Cache Hit: false
Similarity: 0.23
Cache Strategy: pixel-diff
Threshold: 0.05
AI Response Element: null

Stack Trace Cleaning

Stack traces are automatically cleaned to remove internal SDK frames (Element.*, sdk.js internals), showing only your test code for easier debugging.

AIError

Thrown when act() exhausts all retry attempts.

javascript

try {
  await testdriver.act('perform complex workflow', { tries: 3 });
} catch (error) {
  if (error instanceof AIError) {
    console.log(error.task);       // "perform complex workflow"
    console.log(error.tries);     // 3
    console.log(error.duration);  // 15234 (ms)
    console.log(error.cause);     // underlying Error
  }
}

Properties

<ParamField path="name" type="string"> Always `"AIError"`. </ParamField> <ParamField path="message" type="string"> Enhanced message with execution details block. </ParamField> <ParamField path="task" type="string"> The task description passed to `act()`. </ParamField> <ParamField path="tries" type="number"> Number of attempts that were made. </ParamField> <ParamField path="maxTries" type="number"> Maximum number of attempts configured. </ParamField> <ParamField path="duration" type="number"> Total execution time in milliseconds. </ParamField> <ParamField path="cause" type="Error | undefined"> The underlying error that caused the final failure. </ParamField> <ParamField path="timestamp" type="string"> ISO 8601 timestamp of when the error was created. </ParamField>

Enhanced Message

code

AI failed: Element not found after 3 attempts

=== AI Execution Details ===
Task: perform complex workflow
Tries: 3 / 3
Duration: 15234ms
Cause: ElementNotFoundError: Element not found: "submit button"

Internal Error Classes

These errors are used internally by the agent and are not exported, but may appear as the cause of an AIError:

MatchError

Thrown when element matching fails (text, image, or assertion).

Property	Type	Description
`fatal`	`boolean`	If `true`, cannot be healed. Default: `false`
`attachScreenshot`	`boolean`	Always `true` — a screenshot is attached to the error

CommandError

Thrown for invalid arguments or unsupported operations.

Property	Type	Description
`fatal`	`boolean`	Always `true`
`attachScreenshot`	`boolean`	Always `false`

Soft Assert Mode

Inside act(), assertions run in soft assert mode. When an assertion fails, it returns the failure result instead of throwing, allowing the AI to process the failure and adjust its approach.

javascript

// Inside act(), assertion failures don't throw
await testdriver.act('verify the dashboard shows correct data', {
  tries: 3,
});
// The AI can see assertion results and self-correct

This is automatic — you don't need to configure it. Regular assert() calls outside of act() will throw normally on failure.

Error Handling Patterns

Catching Specific Errors

javascript

import TestDriver, { ElementNotFoundError, AIError } from 'testdriverai';

try {
  await testdriver.find('submit button').click();
} catch (error) {
  if (error instanceof ElementNotFoundError) {
    // Element wasn't found — check screenshot for debugging
    console.log('Debug screenshot:', error.screenshotPath);
  } else if (error instanceof AIError) {
    // AI exhausted retries
    console.log(`Failed after ${error.tries} tries in ${error.duration}ms`);
  } else {
    throw error; // Unexpected error
  }
}

Using Debug Screenshots

javascript

try {
  const el = await testdriver.find('checkout button');
  await el.click();
} catch (error) {
  if (error instanceof ElementNotFoundError) {
    // Screenshot of what the screen looked like
    console.log('Screen:', error.screenshotPath);
    // Pixel diff showing cache comparison
    console.log('Diff:', error.pixelDiffPath);
    // Full AI response metadata
    console.log('AI:', JSON.stringify(error.aiResponse, null, 2));
  }
}

Types

typescript

class ElementNotFoundError extends Error {
  name: 'ElementNotFoundError';
  description: string;
  screenshotPath: string | null;
  pixelDiffPath: string | null;
  cachedImagePath: string | null;
  aiResponse: Record<string, any> | null;
  timestamp: string;
}

class AIError extends Error {
  name: 'AIError';
  task: string;
  tries: number;
  maxTries: number;
  duration: number;
  cause?: Error;
  timestamp: string;
}